This invention relates to systems for heating, cooling, humidification and heat recovery ventilation.
To date, heating, cooling, humidification and heat recovery ventilation (HRV) have been accomplished by using three or even four separate pieces of equipment. In the situation where four pieces of equipment are used, the common method would include a standard fossil fuel type furnace, a central or window air-to-air type air conditioner, a duct mounted humidifier and a heat recovery ventilator (HRV). When three pieces of equipment are used the heating and cooling system would be one of the components, generally referred to as a geothermal or air-to-air reversible heat pump, while the humidification and heat recovery ventilation would be accomplished with two separate pieces of equipment. In the aforementioned instances the ducting, condensate draining, wiring, fusing and controls are needed for each system individually. There is no way to increase the efficiency with existing systems because they are separate components, so the capital cost and operating efficiencies which could be gained by integration are not available.
The presently available HRV equipment commonly uses a passive cross-flow core or a desiccant wheel core or a Freon-filled direct exchange core, complete with various types of defrost methods. The defrost methods presently available include an electric defrost or various configurations of damper defrost. The electric defrost element which is usually located in the fresh air supply stream generally starts to operate at approximately xe2x88x925 degrees C. (23 degrees F.). It will then cycle on and off until xe2x88x9215 degrees C. (5 degrees F.) at which time it is on until the temperature warms up to above xe2x88x9215 degrees C. (5 degrees F.). The electric defrost method is obviously inefficient from an operating cost perspective because of the cost to run the electrical elements. The damper type defrost is more widely accepted, as the method of choice. However, there are drawbacks to the existing systems. One method of damper defrost includes closing a damper on the fresh air intake while opening a damper to draw pre-warmed air from the inside of the space. As the pre-warmed air flows through the HRV core, it defrosts the core. Since the exhaust motor still continues to operate, this method causes an unbalanced system, causing a negative pressure in the space while the system is in the defrost mode. Another damper defrost method includes opening a damper within the HRV and re-directing the stale air to the outside to the fresh air intake section. Although this system does not cause the unwanted negative pressure problem, it will cause a problem where the stale exhaust air will be sent to the living area of the space along with all odors common in stale air.
Present day humidifiers use several methods of humidification and controls. The most common type of humidifier includes a return air duct mounted system complete with a humidistat for control. For example, when the humidity level drops to 45% in the winter, the humidistat sends power from an externally mounted transformer to a small, slowly revolving 24V motor which is attached to a wheel wrapped in a sponge-like material (sponge wheel). The sponge wheel is slightly immersed in a water pan. The water is normally taken from a saddle tee located on one of the water lines close to the unit. The sponge wheel soaks up some of the water from the pan as it is revolving. When the pan""s water level drops below a pre-set level, then a shut-off float mechanism, mounted to the pan, opens to allow more water into the pan. As the pan fills with water, the float closes and stops, allowing water to flow into the pan. When the return air runs over the sponge wheel, it pulls some of the water into the air stream, thus humidifying the air stream and thereby increasing the humidity level within the space. This system can cause moisture problems which generally result from calcification of the float control and sponge wheel. Control problems and water leakage into the furnace are common within presently offered humidifiers.
It is presently well known that heating and cooling can be accomplished with a geothermal or air-to-air compression-based heating and cooling system, or a reversible, mechanical vapor compression system, hereinafter referred to simply as xe2x80x9cheat pumpsxe2x80x9d. These reversible, mechanical vapor compression systems or heat pump systems have been utilized to accomplish the goal of efficiently heating and cooling together within a unitary reversible system. An air-to-air heat pump absorbs energy and rejects energy to the outdoor air. The application for an air-to-air heat pump in northern climates is limited because when the outdoor air temperature drops below a prescribed level (usually 40 degrees F.), the system cannot pump any further heat out of the air. The cooling side of an air-to-air heat pump does not offer the highest efficiency as achieved with a geothermal heat pump, but can be effective in most temperature ranges. The capital cost of an air-to-air heat pump is lower but again the operating efficiencies suffer in comparison to a geothermal heat pump. Although the capital cost is higher, the popularity of geothermal heat pumps has grown dramatically over the years because of the constant underground temperature and the much higher efficiency levels.
At present, a geothermal heat pump absorbs and rejects energy from underground or fresh water source, in distinctly different ways. It either uses a closed horizontal or vertical ground or lake loop, or it can absorb or reject energy directly from a domestic well or water source on the property. Together, these are hereinafter referred to as xe2x80x9cgeothermal underground energy sourcesxe2x80x9d.
If the geothermal underground energy source is based on a horizontal closed loop method it includes the use of polyethylene pipe, which is buried in trenches in a horizontal configuration in rows or circuits approximately one foot below the frost level. A closed lake or river loop uses the same polyethylene pipe, but instead of burying the pipe underground as with a horizontal loop, it is simply sunk to the bottom of the. river or lake and adhered to a pre-configured plastic fence matting material. A vertical closed loop involves drilling bore holes down into the ground, all to the same specific depths, inserting polyethylene pipe into the bore holes and connecting them as circuits inside of a trench which links each set of pipes. The circuits are designed to reduce pressure drop to an acceptable level thereby causing the appropriate flow rates. The loop is hooked to two three-way purging valves at the unit. One or two low-voltage pumps are installed in the loop to cause the flow of the liquid within the closed loop. The fluid that is commonly used in a closed loop system includes a mixture of an environment-friendly and government-approved anti-freeze solution along with water. The water and anti-freeze solution is pumped from and to a Freon-to-liquid evaporator/condenser (hereinafter referred to as a xe2x80x9cliquid heat exchangerxe2x80x9d), by the low voltage pumps at a specified flow rate, causing specific energy absorption or rejection, depending on the mode of operation. The liquid heat exchanger uses Freon within a refrigeration system to pump the energy from the geothermal underground energy source to the indoor Freon-to-air heat exchanger.
If the geothermal energy source is based on an open-well water source, or internal loop in a commercial building water source, the common method of absorbing or rejecting energy is to hook the liquid heat exchanger directly to the available water source. The water is usually pumped in and out of the liquid heat exchanger by the pre-existing water pressure system. In the case of a commercial building which uses an internal closed loop system, the water would be piped and pumped via the pre-existing system. In the case of a residential application in a rural setting the existing well pump would be used to pump water from the well into and out of the Freon-to-liquid heat exchanger at a prescribed flow rate. Then it is sent to a discharge point somewhere else on the property but at the same aquifer level. When the discharge is pumped out to the same aquifer level, it is generally believed that the water will make its way underground back to the well after it picks up energy from underground. In a situation where a geothermal heat pump (sometimes called a water source heat pump) is used in a high rise or a zoned commercial complex there are various methods of taking advantage of the underground energy sources as well as above-ground energy sources. In this case the geothermal or water source heat pump is used as an energy transfer mechanism where a unit is placed in each zone and tied to a common underground loop, common internal loop, or open-well system. There are presently many such applications in existence.
A geothermal heat pump is considered very reliable, given that ground and underground water temperatures do not generally fluctuate to the same extent as outdoor air temperatures. An air-to-air heat pump offers a co-efficient of performance (COP) compared to electric heating of approximately 1.8 to 1, depending on outdoor temperature conditions. However, when the outdoor air temperature drops below a specified level, then the heating side of an air-to-air system switches over to straight electric, thereby reducing the efficiency to a COP of 1 to 1. The same is true for an air-to-air system in the cooling mode; when the air temperature increases beyond 95 degrees F. outdoors, the COP is lowered. A geothermal heat pump offers a much higher COP, approximately 3.5 to 1, regardless of the outdoor temperatures.
Again, although the capital cost of a geothermal or water source heat pump is higher than for an air-to-air heat pump, the operating cost savings of geothermal make it a wise choice. However, both systems make economic sense under the right conditions. Both configurations are referred to herein as xe2x80x9cheat pump or reversible vapor compression systems, or reversible compression based heating and cooling systemsxe2x80x9d.
Regarding HRV systems, xe2x80x9csick building syndromexe2x80x9d has become a common term within the building industry. It relates to the fact that as the thermal envelopes of buildings are getting tighter (higher R-values, better air barriers, therefore less air leakage), the possibility of stale air causing health problems for the occupants is much more prevalent and a major concern to designers. A tight building will also cause a problem when humidity stays in the building and is not properly ventilated. Humidity can cause significant degradation to the building itself. Humidity problems are well documented and generally accepted as a design issue in most building codes (residential and commercial). Humidity will come from several sources including the occupants. These problems demand ventilation. As ventilation is incorporated into the building designs, the recovery of energy becomes more and more important, as a cost and efficiency issue and in most cases necessary by the various municipal building codes. Although there are many, many environmental benefits, the product must make economic sense.
In view of the above, it is an object of the invention to provide an integrated system for heating, cooling and heat recovery ventilation, in which a heat pump or a reversible vapor compression system or a compression based heating and cooling system is integrated with a high efficiency heat recovery ventilation system, and optionally with an on-board humidification system.
The heat recovery ventilation section of the equipment offers either a base efficiency passive cross flow air-to-air heat exchanger core (hereinafter referred to by the abbreviation xe2x80x9cPCAAHECxe2x80x9d) and if required, a secondary high-efficiency, active, reversible refrigeration based evaporator/condenser heat exchanger. The preferred compression based heating and cooling system portion uses geothermal energy, but the invention is also applicable to the use of an air-to-air heat pump. Both systems make economic sense under the right conditions.
Since only one supply air ducting system is used, the integrated system offers every room in the occupied space a proportionate amount of pre-mixed fresh air without the need for two sets of ducts.
Besides offering the standard primary cross flow heat exchange core, the integrated system can incorporate an optional, high efficiency secondary active refrigerant based energy recovery coil within the ventilation function of the system. The secondary active refrigerant based energy recovery core would only be used when the compression based heating, cooling system is operating.
The capital cost and operating efficiencies will increase in the heat recovery, heating and cooling modes over that which is presently available as separate components because of the integration. The system will very efficiently heat, cool and ventilate at a prescribed rate while simultaneously extracting energy prior to the stale air removal. Variously configured defrost methods can be employed without causing the negative pressure and/or odor transferring problems, as described in the prior art section above. When the integrated system goes into the defrost mode it can use the aforementioned damper control system, but the associated problems can be eliminated because the exhaust fan can be electronically turned on or off independently, which is a feature not available in presently offered equipment.
The integration in the present invention allows for a standard primary crossflow core and an active secondary refrigerant exchanger core.
Since an aluminum and copper coil is used complete with a drain pan and drain pan sensor within the compression based heating and cooling portion of the integrated system, the associated leakage problems common in the prior art, can be avoided, and the general cost is reduced. The vapor is atomized upstream of the coil, and then as it hits the warmed coil it immediately evaporates because the air coil runs at a temperature well above the evaporation point. The humidification section of the system only operates when the heating and cooling section is operating in the heating mode.
Such an integrated system offers some or all of the following advantages over the prior art:
general efficiency increase
a generally healthier indoor environment
one system to install as compared to three or four
less installed space needed
one extra fan for the HRV as compared to three or four
more control over the operating fans
better mixing and supply of fresh and heated or cooled air to each room
one control system as compared to three or four
increased efficiency in the heating mode
increased efficiency in the cooling mode
increased efficiency in the HRV Mode
better defrost without causing negative pressure or transferring odor to space
better humidity control
one main power connection complete with internal down fusing